Pricorde, I back that 100%. Runge Kutta integrators are well suited to problems of e.g. celestial mechanics (although these days it's done in much fancier ways) where the forces are smoothly varying. RK beats Euler in the sense that the error is about the square of the error of the Euler method, so if an error is small, its square is even moreso. But this analysis is all fine and well as long as the forces etc. vary sufficently smoothly over time, which in games is very rarely the case. It may well be that the RK could perform even worse in terms of stability if sudden collisions etc. are taken into account, there is no inherent reason why it should perform any better than Euler. Since absolute accuracy of the solution in a game isn't even a priority (since the trajectory is all the time controlled by the player anyway) I don't think that for game application there's real incentive to use Runge Kutta, especially since Euler can be tailored to treat some exceptional cases such as collisions much more easily.
Well, you are right with the last point, but this IS Windows we are talking about
. It could be a silly thing such as the automatic updates going off, or any other services that can momentarily stutter your game (and most games are susceptible to such stutter). The point isn't so much in the simulation killing itself, the point is that you aren't simulating the same thing anymore if the framerate is different. There is always an error associated with discretization schemes, and the error is always larger the longer the timestep. In an online racing game, a person running at 30fps will experience slightly different physics than the person running at 100fps, which will give either of the two an unfair advantage (depending on how the errors affect the physics), and this is without taking into account the fact that the person with 100fps will have an advantage anyway. But, as Scawen says, that is really not the most important reason why high frequency of updates is necessary in any case. It is the stiffness in a system that leads to high frequencies, which themselves require short timesteps in order to not blow up. There are ways to run stiff systems with timesteps that are (much) longer than what would normally be required, but this is really a whole new can of worms altogether. Not to mention, if there is a bug in the physics code (there always is one ) you can never be sure if it's because FPS is fluctuating wildly or something else is going on. In my opinion, the best way to go about doing things is keeping the timestep of physics updates absolutely constant, and in each cycle running enough iterations of the physics code to catch up with the real time clock, rendering the result, lather, rinse, repeat.
Becky, there is one nasty problem with the way you suggest, namely that the physics behaviour may be linked to the frame rate. Suppose the frame rate stays at, say 100, but for whatever reason it drops for a second or so to below 10. This can really throw your calculations off if you're doing just one update per frame, even if you are not handling stiff systems such as what Scawen mentions, if nothing else the collisions is what will get you.
This is quite a common debate in many sim-racing forums, and usually there's two camps that emerge. The first one is the "mass market" part of the community, who for the most part agree that the force feedback wheels provide a much better experience than any non-force feedback device in a similar price range. On the other side, there is the people who invested a small fortune into their non-ff high end setups and claim (much like the marketing material for those wheels) that force feedback is a technology that at this point only detracts from the overall experience. From both sides of the debate, it seems to me that for the most part the people are trying to justify their purchase decision, and this goes doubly (or is it ten-fold :P ) so for the high-end non force feedback wheels.
In my opinion, if it is fastest laptimes you are looking at, force feedback will never help you in this respect and may indeed even hinder you. Although it would be fair to say that it is actually the pedals that come with most mass-market wheels is what will hinder you most, especially the brake one (if you are not running ovals :P ). I also do not find it surprising that people who have non-ff wheels and try the ff ones will find them awkward. The reason for that is that they are simply having to recalibrate their inputs as they got used to driving without the simulated forces on the wheel, much like driving a real car requires a different control loop from a driver than sim racing does, as the feedback from your bottom tells you an additional fair bit about what's happening.
I believe that FF actually provides a rather significant additional signal for the sim-racer. It will not help you improve your laptime, but what it does is help you in the situations where you overstep the limits. I find that, for example, opposite lock, which comes completely naturally with force feedback just as it does in a real car, is a serious guessing exercise without it. Now, although I am sure that with enough practice it can be done just as efficiently without FF as it can be with it (I do remember doing that easily in the old GPL days), it is important to note that in one case it requires a lot of determined effort to improve on it, and in the FF case it's something you don't give another thought. While it is true that FF might slow down some of the very quickest inputs, I never felt that it would be a hindrance myself (hey, I am getting old, no such fast inputs possible anymore ) and on the other hand, especially since the wheel is already helping you move in the proper direction once a quick input is required, and that goes even across the center in the opposite lock situation.
I would say that FF still has a long way to go, but as it is now, to an average sim racer it provides so much more feedback and immersion that it would be a shame not to use it. In the future, I do hope a system that is not based on electric motors but perhaps some electromagnets or similar might provide less resistance and a smoother drive, and at that point there will be no point in not using FF at all.
In my opinion, if it is fastest laptimes you are looking at, force feedback will never help you in this respect and may indeed even hinder you. Although it would be fair to say that it is actually the pedals that come with most mass-market wheels is what will hinder you most, especially the brake one (if you are not running ovals :P ). I also do not find it surprising that people who have non-ff wheels and try the ff ones will find them awkward. The reason for that is that they are simply having to recalibrate their inputs as they got used to driving without the simulated forces on the wheel, much like driving a real car requires a different control loop from a driver than sim racing does, as the feedback from your bottom tells you an additional fair bit about what's happening.
I believe that FF actually provides a rather significant additional signal for the sim-racer. It will not help you improve your laptime, but what it does is help you in the situations where you overstep the limits. I find that, for example, opposite lock, which comes completely naturally with force feedback just as it does in a real car, is a serious guessing exercise without it. Now, although I am sure that with enough practice it can be done just as efficiently without FF as it can be with it (I do remember doing that easily in the old GPL days), it is important to note that in one case it requires a lot of determined effort to improve on it, and in the FF case it's something you don't give another thought. While it is true that FF might slow down some of the very quickest inputs, I never felt that it would be a hindrance myself (hey, I am getting old, no such fast inputs possible anymore
) and on the other hand, especially since the wheel is already helping you move in the proper direction once a quick input is required, and that goes even across the center in the opposite lock situation.I would say that FF still has a long way to go, but as it is now, to an average sim racer it provides so much more feedback and immersion that it would be a shame not to use it. In the future, I do hope a system that is not based on electric motors but perhaps some electromagnets or similar might provide less resistance and a smoother drive, and at that point there will be no point in not using FF at all.
Well, it's Dr. Veble, but otherwise pretty much spot on...
Those are the easiest to dispose of, the trick is to actually give them more room rather than staying as close to the usual line as possible. Since they already braked late this means that they will invariably take a very early apex and will not be able to carry much speed out of the corner. To counter, let the kamikaze through on the inside, brake perhaps even a tad longer and go wider than usual on entry so that the other driver is already through, but then, after turning in, start accelerating earlier with a later apex than ideal. You will of course loose some time overall but will gain a much better exit speed, making the kamikaze driver an easy target on the straight after the corner, assuming that he or she will make the corner in the first place
.Excuse me, but questioning the value of my Ph.D. and comparing me to people who you seem not to have much regard for is an insult. Not an insult that I would be particularly affected by, mind you, it is simply that this is not the level of conversation I accept.
And debating scientific concepts that may or may not have any merit is not an insult; it is the very essence of science. I will withdraw myself from this discussion here (it is OT anyway), but I would be quite glad if, after you obtain your degree, which I am sure you will have no trouble obtaining as you appear rather smart, you think back upon this discussion and see if your opinions are still as clearcut.
George,
first of all, knock it off with insults. Second, be mindful of the phrase, "a little knowledge is a dangerous thing." I am in awe almost every day as to the things I still yet have to learn about, and not for one second have any Faustian beliefs that I already know all the knowledge in the world. Choose to do otherwise at your own academic peril.
It is no way to argue that we are not talking about GR here. It is slightly metaphysical concepts we are debating (as an apple will always fall with 1g regardless of whether we assume gravity is an acceleration or a force) and to build any sort of philosophy on science one needs to look at its most fundamental theories. Just as concepts of determinism shatter when employing quantum mechanics (whereas in Newtonian physics the future is in principle exactly determined from the exact starting conditions, barring concepts of chaos), general relativity turns our concept of gravity, space and time on their head.
In general relativity, the space shuttle is said not to be in accelerated motion in orbit around the Earth, but that it is rather following a straight line through curved spacetime. As such it is locally not experiencing any acceleration. It is conceptually much simpler to describe motion that way, even if it is counterintuitive. If such a description also helps understand other phenomena like the peculiarities of the trajectory of Mercury, then the theory is surely to be considered more fundamental than the one preceeding it. Occam's razor will get you anytime.
And gravity is NOT just like one of the other fundamental interactions. All the other interactions take spacetime as the underlying concept which they are formulated upon. Gravity on the other hand is responsible for the very behaviour of spacetime. Attempts to write down (quantum) gravity as a similar field theory to other interactions did not yield any tangible results so far, although they produced a lot of interesting mathematics on the side (string theory). It is precisely because gravity is unlike anything else that this remains one of the large open problems of theoretical physics.
Kidcodea, actually, I am going to Vienna to assa..... err discuss things with Todd as he ... knows ... too ... much.
Todd, nah, those are just my latest papers, I almost forget what I did in my Ph.D. thesis.
first of all, knock it off with insults. Second, be mindful of the phrase, "a little knowledge is a dangerous thing." I am in awe almost every day as to the things I still yet have to learn about, and not for one second have any Faustian beliefs that I already know all the knowledge in the world. Choose to do otherwise at your own academic peril.
It is no way to argue that we are not talking about GR here. It is slightly metaphysical concepts we are debating (as an apple will always fall with 1g regardless of whether we assume gravity is an acceleration or a force) and to build any sort of philosophy on science one needs to look at its most fundamental theories. Just as concepts of determinism shatter when employing quantum mechanics (whereas in Newtonian physics the future is in principle exactly determined from the exact starting conditions, barring concepts of chaos), general relativity turns our concept of gravity, space and time on their head.
In general relativity, the space shuttle is said not to be in accelerated motion in orbit around the Earth, but that it is rather following a straight line through curved spacetime. As such it is locally not experiencing any acceleration. It is conceptually much simpler to describe motion that way, even if it is counterintuitive. If such a description also helps understand other phenomena like the peculiarities of the trajectory of Mercury, then the theory is surely to be considered more fundamental than the one preceeding it. Occam's razor will get you anytime.
And gravity is NOT just like one of the other fundamental interactions. All the other interactions take spacetime as the underlying concept which they are formulated upon. Gravity on the other hand is responsible for the very behaviour of spacetime. Attempts to write down (quantum) gravity as a similar field theory to other interactions did not yield any tangible results so far, although they produced a lot of interesting mathematics on the side (string theory). It is precisely because gravity is unlike anything else that this remains one of the large open problems of theoretical physics.
Kidcodea, actually, I am going to Vienna to assa..... err discuss things with Todd as he ... knows ... too ... much.
Todd, nah, those are just my latest papers, I almost forget what I did in my Ph.D. thesis
.Ok, allow me to chip in a few. Since titles are being thrown about in this thread, let me state for the record that I have a Ph.D. in physics, and I work in theoretical physics.
It was one of the great mysteries of classical physics as to why apples fall as fast as cars off a cliff (in vacuum, and forgetting there were no cars at the time). While the Newton's gravity formula shows that such behaviour is indeed the case, it is a mere postulate without any explanation. The fact as to why the mass entering the forumula for gravitational force and the one entering the acceleration formula (F=m*a) are the same (the so called gravitational and inertial mass equivalence) was unexplained.
Enter a bright young lad named Einstein. He observed the same as what we are arguing now, namely that one really can't sense properly whether it's the effects of gravity one is feeling or if it is acceleration. He actually had the light bulb moment upon realizing that free falling is basically the same as being weightless. A bit of mathematics later (well, that was the crucial, hard and time consuming part) and he was able to show that starting with the ideas of special relativity and, importantly, equivalence between gravity and acceleration one can explain the gravitational force (as per Newton) and also go beyond that, predicting phenomena that have subsequently been tested to be true. Gravity is interpreted as being due to curvature of spacetime. This theory goes by the name of general theory of relativity and is still largely baffling even the smartest physicists, as noone knows yet how to merge it with quantum stuff.
While the whole discussion is really semantics and somewhat metaphysical (theories taken at face value are there just to predict stuff, giving them more meaning borders on religion), the simple fact that such a simple premise that Einstein took can yield so much more insight than previously imaginable, shows that there is some merit to the idea that, indeed, gravity is acceleration. More precisely, standing still in a gravitational field is the same as accelerating upwards with no field present.
So Todd, your hunch was a rather good one all along, seeing it lead to great ideas in the past. Of course, you had it easier, as Einstein didn't have high performance cars to drive and check those effects more easily. See you in Vienna soon!
It was one of the great mysteries of classical physics as to why apples fall as fast as cars off a cliff (in vacuum, and forgetting there were no cars at the time). While the Newton's gravity formula shows that such behaviour is indeed the case, it is a mere postulate without any explanation. The fact as to why the mass entering the forumula for gravitational force and the one entering the acceleration formula (F=m*a) are the same (the so called gravitational and inertial mass equivalence) was unexplained.
Enter a bright young lad named Einstein. He observed the same as what we are arguing now, namely that one really can't sense properly whether it's the effects of gravity one is feeling or if it is acceleration. He actually had the light bulb moment upon realizing that free falling is basically the same as being weightless. A bit of mathematics later (well, that was the crucial, hard and time consuming part) and he was able to show that starting with the ideas of special relativity and, importantly, equivalence between gravity and acceleration one can explain the gravitational force (as per Newton) and also go beyond that, predicting phenomena that have subsequently been tested to be true. Gravity is interpreted as being due to curvature of spacetime. This theory goes by the name of general theory of relativity and is still largely baffling even the smartest physicists, as noone knows yet how to merge it with quantum stuff.
While the whole discussion is really semantics and somewhat metaphysical (theories taken at face value are there just to predict stuff, giving them more meaning borders on religion), the simple fact that such a simple premise that Einstein took can yield so much more insight than previously imaginable, shows that there is some merit to the idea that, indeed, gravity is acceleration. More precisely, standing still in a gravitational field is the same as accelerating upwards with no field present.
So Todd, your hunch was a rather good one all along, seeing it lead to great ideas in the past. Of course, you had it easier, as Einstein didn't have high performance cars to drive and check those effects more easily
. See you in Vienna soon!FGED GREDG RDFGDR GSFDG